It’s clever but still creepy: Facebook is exploring partnerships with data companies that provide loyalty cards to retailers like drug stores and retailers in order to show you ads based on your shopping habits.

As AdAge reports, Facebook may obtain the phone numbers and email addresses that customers supply to drug stores in return for discounts and loyalty points. The company will then match the numbers and emails with user Facebook profiles in order to create new marketing opportunities. This means, for instance, that I might buy ex-lax at the store and then see ads for All-Bran in my Facebook feed.

This merging of online and offline data creates powerful marketing opportunities and, as ad industry people like to point out, will let people see ads they’re theoretically interested in seeing. In this perfect world of data-based marketing, no company will waste their money showing baby food or make-up ads to the likes of me — and I will be happier because I don’t have to see those ads.

The flip side, of course, is the creepy factor. Facebook and the data companies (in this case Epsilon, Acxiom and Datalogix) do take care to protect so-called “PPI” (protected personal information) by scrubbing out names and just using other techniques to make the data anonymous. But one still shudders about the unencrypted information escaping into the wild through carelessness or hacking. In my case, it just increases my resolve to provide retailers with fictitious names and numbers.

For now, we may still be a ways of from the onslaught of fiber ads in our Facebook. According to AdAge, the new “custom audience” options are still winding their way through nervous corporate legal departments.